Commit f4eef224 authored by Angelo Dureghello's avatar Angelo Dureghello Committed by Greg Kroah-Hartman
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serial: fsl_lpuart: add sysrq support when using dma 



Add handling of magic sysrq keys when using dma/edma.

Tested by sending BREAK followed by a sysrq command inside
a 5 secs time window, by:

echo 1 > /proc/sys/kernel/sysrq

BREAK + h, t, e, b, c

Tested also sending a command after 5 secs after BREAK, that's
properly ignored.

Signed-off-by: default avatarAngelo Dureghello <angelo.dureghello@timesys.com>
Link: https://lore.kernel.org/r/20201004161144.1307174-1-angelo.dureghello@timesys.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent bfeb2853

drivers/tty/serial/fsl_lpuart.c

+57 −0
Original line number Diff line number Diff line
@@ -976,6 +976,15 @@ static irqreturn_t lpuart_int(int irq, void *dev_id) 


	sts = readb(sport->port.membase + UARTSR1);



	/* SysRq, using dma, check for linebreak by framing err. */

	if (sts & UARTSR1_FE && sport->lpuart_dma_rx_use) {

		readb(sport->port.membase + UARTDR);

		uart_handle_break(&sport->port);

		/* linebreak produces some garbage, removing it */

		writeb(UARTCFIFO_RXFLUSH, sport->port.membase + UARTCFIFO);

		return IRQ_HANDLED;

	}



	if (sts & UARTSR1_RDRF && !sport->lpuart_dma_rx_use)

		lpuart_rxint(sport);
@@ -1004,6 +1013,37 @@ static irqreturn_t lpuart32_int(int irq, void *dev_id) 
	return IRQ_HANDLED;

}





static inline void lpuart_handle_sysrq_chars(struct uart_port *port,

					     unsigned char *p, int count)

{

	while (count--) {

		if (*p && uart_handle_sysrq_char(port, *p))

			return;

		p++;

	}

}



static void lpuart_handle_sysrq(struct lpuart_port *sport)

{

	struct circ_buf *ring = &sport->rx_ring;

	int count;



	if (ring->head < ring->tail) {

		count = sport->rx_sgl.length - ring->tail;

		lpuart_handle_sysrq_chars(&sport->port,

					  ring->buf + ring->tail, count);

		ring->tail = 0;

	}



	if (ring->head > ring->tail) {

		count = ring->head - ring->tail;

		lpuart_handle_sysrq_chars(&sport->port,

					  ring->buf + ring->tail, count);

		ring->tail = ring->head;

	}

}



static void lpuart_copy_rx_to_tty(struct lpuart_port *sport)

{

	struct tty_port *port = &sport->port.state->port;
@@ -1090,6 +1130,15 @@ static void lpuart_copy_rx_to_tty(struct lpuart_port *sport) 
	 */

	ring->head = sport->rx_sgl.length - state.residue;

	BUG_ON(ring->head > sport->rx_sgl.length);



	/*

	 * Silent handling of keys pressed in the sysrq timeframe

	 */

	if (sport->port.sysrq) {

		lpuart_handle_sysrq(sport);

		goto exit;

	}



	/*

	 * At this point ring->head may point to the first byte right after the

	 * last byte of the dma buffer:
@@ -1121,6 +1170,7 @@ static void lpuart_copy_rx_to_tty(struct lpuart_port *sport) 
		sport->port.icount.rx += count;

	}



exit:

	dma_sync_sg_for_device(chan->device->dev, &sport->rx_sgl, 1,

			       DMA_FROM_DEVICE);
@@ -1557,6 +1607,7 @@ err: 
static void lpuart_rx_dma_startup(struct lpuart_port *sport)

{

	int ret;

	unsigned char cr3;



	if (!sport->dma_rx_chan)

		goto err;
@@ -1573,6 +1624,12 @@ static void lpuart_rx_dma_startup(struct lpuart_port *sport) 
	sport->lpuart_dma_rx_use = true;

	rx_dma_timer_init(sport);



	if (sport->port.has_sysrq) {

		cr3 = readb(sport->port.membase + UARTCR3);

		cr3 |= UARTCR3_FEIE;

		writeb(cr3, sport->port.membase + UARTCR3);

	}



	return;



err:

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